Wholesale conversion to #pragma once

Kudos to cgmb and https://github.com/cgmb/guardonce

Change-Id: Ifa8970734b8d43fd08c9260c645bdb0228633791
Reviewed-by: Tobias Hunger <tobias.hunger@theqtcompany.com>

src/libs/qtcreatorcdbext/stringutils.h

@@ -23,8 +23,7 @@
 **
 ****************************************************************************/
 
-#ifndef STRINGUTILS_H
-#define STRINGUTILS_H
+#pragma once
 
 #include <string>
 #include <sstream>
@@ -222,5 +221,3 @@ void formatGdbmiHash(std::ostream &os, const std::map<std::string, std::string>
 
 // Hex encoding helpers
 void hexEncode(std::ostream &str, const unsigned char *source, size_t sourcelen);
-
-#endif // STRINGUTILS_H